VENOMOUS ANIMALS AND THEIR TOXINS — RUSSELL 485 



tension; it produces broncliial spasms and changes at the neuromuscu- 

 lar junction. Plate 2, iig, 1, shows the tarantula. 



The venoms of some scorpions paralyze; they are among the most 

 eli'ective of the neuromuscular blocking toxins. The venoms of some 

 of the parastic wasps are also jjotent nerve-muscie blocking agents. 

 They are callable of paralyzing the junction in the body muscle masses 

 of their host while having no eii'ect on visceral musculature ; the heart 

 of the paralyzed host may beat for many weeks. The toxicity of 

 some of these venoms is comparable with that of the bacterial toxins. 

 Beard has estimated that 1 part of Braoon hebetor venom in 200 million 

 parts of the host's blood is suthcient to produce paralysis in a late instar 

 larva. 



AH of the tish venoms studied to date are known to be used by 

 venomous lishes in their defense, particularly against those animals 

 which feed upon them. On the basis of our tindings in man it is 

 assmned that lish venoms are capable of producing a similar degree 

 of excruciatmg pam in other animals. 1 have injected small doses 

 of a number of diiferent venoms uito myself and have f omid none quite 

 as painful as those of the stingi'ay and scorpion hshes. A pain- 

 producing substance in the venom of the stingray, and other such 

 venomous fishes (pi. 2, fig. 2), would appear to be a great asset to 

 those fishes in their defensive armament. 



There seems little doubt that the "convulsions'' seen following 

 stringray injuries, as reported by some of the early writers, were prob- 

 ably no more than reactions of hyperactivity provoked by the painful 

 etiects of the venom, rather than responses due to the direct effects 

 of the venom on the central nervous system. This venom does not 

 appear to elicit specific changes in the central nervous system except 

 as secondary effects of cardiovascular changes. Stingray venom, and 

 the toxins of many poisonous fishes, have a direct effect on the pace- 

 maker of the heart, as well as on several other parameters of the car- 

 diovascular system. Both small and large doses of this venom 

 produce a hypotensive crisis in mammals. Small amounts of the 

 venom appear to cause peripheral vasodilation while large amounts 

 cause vasoconstriction. The venoms of the stingrays and weeverfishes 

 (pi. 2, fig. 2) do not appear to have any effect on neuromuscular 

 transmission. 



Snake- venom poisoning constitutes a serious medical problem in 

 some areas of the world. In Asia, excluding Chma, a few years ago 

 approximately 30,000 deaths from snakebites were reported annually. 

 Most of these deaths were due to bites by the cobras Naja naja and 

 Ophiophagus hamiah^ the kraits Bungarus candidus and B. fasciatus, 

 and the vipers Vipera russelli and Echis carinatus. In Africa as many 

 as 1,000 deaths a year may be attributed to snakebite. Most of these 

 deaths are due to bites by the adders Bitis arietans and Causus rhom- 



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